Plastic container injection-moulding machine equipped with quick mould-change arrangement

ABSTRACT

An injection molding machine and method of injection molding is provided, in which an upper platen, a moving platen, and a cavity-carrying platen are used. A removable member (cylinder) is provided to limit travel of the moving platen towards the cavity-carrying platen and to support the moving platen.

BACKGROUND OF THE INVENTION

The present invention refers to a specifically intended arrangement anda related utilization process, which are adapted to enable moulds to bechanged in a very short time in injection moulding machines in which thehalf-moulds move in an either vertical or horizontal direction relativeto each other.

In particular, the present invention applies in a preferred manner tomachines adapted for moulding at the same time a plurality of plasticarticles, ie. the so-called “preforms”, are intended for subsequentprocessing by blow moulding into appropriate final containers,especially plastic bottles.

Although reference will be made in the following description, mainly forreasons of greater descriptive convenience, to a machine for mouldingpreforms of plastic material of the vertical-drive type, as this is usedin combination with the preliminary steps of melting and extrusion ofthe plastic material, it will be appreciated that the present inventionshall be understood as applying also to horizontal-drive injectionmoulding machines or even other kinds of uses or applications, as far asthese fall within the scope of the appended claims.

It is generally known in the art that, during the preform mouldingoperation, use is generally made of a moulding machine comprising astationary half-mould, which is firmly joined to the structure of thesame machine, and a moving half-mould, which moves in a verticaldirection and is selectively closable into an appropriate clampedposition against said stationary half-mould.

With reference to FIGS. 1A, 1B, 2A, 2B and 2C, which illustrate thestate of the art, the upper platen 1, whose particular features shallnot be described here since they are already generally known in the art,is associated externally with a moving mould-carrying platen 2, which isin turn connected to the bar 3 that supports the lips 15. The taskperformed by these lips 15 is to form the neck of a respective bottleand, therefore, they are formed of two separable lip members 15 a, 15 bin consideration of the fact that, during the removal of the preformfrom the mould, the neck portion thereof shall be released from its ownmould which is formed exactly by the lips. Due to the neck portion beingactually provided with a number of undercut-like elements, a selectedmeans for effectively releasing the neck portion from its own mould orlip 15 concerns in making it out of two separable members 15 a and 15 b,as illustrated in FIG. 7.

To the upper platen there are removably secured, through the use ofappropriate fastening means, a plurality of male members 6. Furthermore,to this same upper platen 1 there are firmly associated, in a coaxialarrangement with respect to the male members, respective internalcooling tubes 7.

The mould is completed on the bottom by a cavity-carrying platen 4, inwhich there can be noticed a plurality of cavities 8 adapted to befilled with the material that is injected through respective nozzles 9.

The coupling of the upper platen 1 with the cavity-carrying platen 8 isbrought about by means of a plurality of guide columns 13, which arefirmly joined on top to the upper platen 1 and are adapted to slide intoinsertion in respective through-holes 10 appropriately provided in thecavity-carrying platen.

Furthermore, in view of ensuring the required alignments and theparallelism of the movements, even the moving platen 2 is provided withappropriate through-holes 11 adapted to be slidably engaged by the sameguide columns 13.

During the practical operation of the injection moulding machine, itfrequently occurs that such operational conditions arise as to make itnecessary for access to be gained to the male members in order toreplace and/or repair them. As it can most easily be inferred from theillustration in FIGS. 2A, 2B and 2C, when such a need arises for themale members 6 to be replaced and/or repaired, the first thing that mustbe done is to start by separating the moving mould-carrying platen 2from the upper platen 1, in such a manner as to create a gap betweenthose platens. Therefore, proper access can be gained manually to thefastening means so as to act on these so as to release and remove themale members 6.

Now, such an operation can actually be carried out in a quite easy andconvenient manner if there are just a few (ie. not many) of the malemembers and these are further arranged in a single row. If on thecontrary the male members are arranged in several rows, as illustratedin the Figures, then it becomes much more difficult and awkward foranyone to gain access to the male members due to the limited space thatis available for such a purpose, so that the removal and re-assemblyoperation generally turns out to require a much longer time to becompleted.

If the fact is finally taken into due account that, due toproduction-related or market-driven reasons, the need may actually arisefor such male members to be replaced even as frequently as once a day,it can be readily appreciated how each such operation for thereplacement of the male members, which may typically last as many asfour hours, may on the whole turn out to be extremely expensive andtime-wasting.

All these circumstances are largely known to all those skilled in theart, and are recalled here for the sole purpose of more effectivelyintroducing and illustrating the technical context to which the presentinvention relates.

SUMMARY OF THE INVENTION

Based on the above considerations, it is therefore a main purpose of thepresent invention to provide an injection moulding machine whichcomprises the moving platen, the lip-carrying platen and thecavity-carrying platen, and is equipped with an arrangement that enablesthe cavity-carrying platen to be unclamped and moved away from themoving platen by such an extent as to allow access to be gained to themale members in a much more convenient and easy manner, so as todrastically cut down the time required to remove and subsequentlyre-assemble the male members.

The above arrangement shall furthermore be capable of being easilyimplemented using readily available and, therefore, cost-effectivematerials and techniques, and is further easy, reliable and safe to use.

Such an aim of the present invention, along with further featuresthereof, is reached in an injection moulding machine that is made andoperates as recited in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention may take the form of a preferred, although notsole embodiment such as the one that is described in detail andillustrated below by way of non-limiting examples with reference to theaccompanying drawings, in which:

FIG. 1A is a perspective view of some basic parts of an injectionmoulding machine according to the state of the art, in a first operatingstate thereof;

FIG. 1B is an enlarged view, from a different perspective, of a detailof FIG. 1A;

FIG. 2A is a perspective view of the same parts as the ones illustratedin FIG. 1A, however in a different operating state thereof;

FIG. 2B is a perspective view of two of the machine parts illustrated inFIG. 2A, as seen from a different perspective point;

FIG. 2C is a vertical cross-sectional view (A—A) of the injectionmoulding machine illustrated in FIG. 1A;

FIG. 3 is a perspective view of the same parts of the injection mouldingmachine illustrated in FIG. 1A, in which the machine is however providedwith the arrangement according to the present invention;

FIG. 4 is a perspective view of the same parts of the injection mouldingmachine illustrated in FIG. 3, in which the various parts thereof arehowever coupled with each other in a first operating phase according tothe present invention;

FIG. 5A is a perspective view of the same parts of the injectionmoulding machine illustrated in FIG. 4, in which they are howeverarranged in a second operating phase according to the present invention;

FIG. 5B is a different perspective view of the same parts of theinjection moulding machine illustrated in FIG. 5A;

FIG. 6 is a side view, along the direction “B”, of the injectionmoulding machine illustrated in FIG. 5B;

FIG. 7 is an enlarged cross-sectional view of a portion of an injectionmoulding machine provided with an arrangement according to the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

With reference to the above listed Figures, a vertical-drive type ofinjection moulding machine provided with an upper half-mould adapted toproduce preforms of plastic material comprises an upper platen 1, amoving platen 2, and a plurality of lips, or neck-rings as they are alsocalled in the art. The lips are the mould portions that are intended toform the neck portion of the preform during the injection of thethermoplastic resin, and are formed by two respective separable members15 a and 15 b. A support bar 3 carries the plurality of lips, and aplurality of male members 6 are secured at their bottom or foot portionto the upper platen 1 by an appropriate fastening means as they arecommonly known and used in the art.

Furthermore, inside the male members there are preferably providedrespective cooling tubes 7, whose task and structure are generally knownin the art, and which are applied on to the lower face of the upperplaten 1.

The injection moulding machine further comprises a cavity-carryingplaten 4, in which there are provided a plurality of cavities 8associated with respective gates or nozzles 9 through which the moltenresin is actually injected.

The described injection moulding machine is provided also with aplurality of guide columns 13, which are firmly joined on top to theupper platen 1 and are adapted to slidably move into respectiveappropriate through-holes 10 provided in the cavity-carrying platen andinto respective appropriate through-holes 11 provided in the movingmould-carrying platen 2.

The task assigned to the guide columns and the through-holes is toensure correct alignment of the upper platen, the moving mould-carryingplaten, and the cavity-carrying platen with respect to each other whenthey move with respect to each other. On the other hand, these parts aresolely illustrated by way of more effective, thorough exemplification,although not strictly necessary to the purposes of the present inventionand are not anyway a part thereof.

It is largely known that, according to prior-art solutions, in order toreplace the male members in an injection moulding machine of the typedescribed here by way of example, a procedure is usually followedincluding, among other things, the steps of:

releasing the safety pins 21 and clearing the knock-out pins 20;

raising the upper platen up to the highest opening position allowed forby the injection moulding machine itself;

separating the moving platen from the upper platen and lowering it downto a level corresponding to the downward stroke or travel covered toclamp (ie., close) the mould and limited by the length of the columns orpins.

As this has already been said earlier in this description, in such astate of the injection moulding machine it is certainly possible for themale members to be reached for their removal. Under certaincircumstances, however, this may well turn out to be quite awkward andcomplicated.

The presence of the cooling tubes inserted in the male members, andwhich anyhow remain in their position inside the male members, needs tobe furthermore taken into due account, since it becomes necessary forthe male members to be appropriately lowered so as to be able to slipthem off downwards from the respective attachments in the upper platen.In other words, this is an operation that makes it still morecomplicated, awkward and demanding to disengage and subsequentlyre-assemble the male members.

In view of doing away with such a drawback, the present inventionconsists in enabling the moving platen 2 to be lowered down to wellbeyond the usual level, without the constraint of having to retain itanyway engaged to the guide columns 13. As a matter of fact, the abilityof lowering the moving platen to a significantly greater extent wouldenable the gap that is so obtained between the upper platen, whichmaintains its raised position, and the moving platen 2 to be increasedaccordingly.

According to the present invention, such a greater extent of lowering isobtained by providing an appropriate removable member between the movingplaten and the cavity-carrying platen 4, wherein the task assigned tothe removable member lies in constituting appropriate resting means forthe moving mould-carrying platen which can in this way be fullydisengaged from the upper platen 1.

The need for the utilization of the resting means and an adequatelylarge separation of the moving platen from the cavity-carrying platen 4depends on the circumstance that there is provided a cam-operatedmechanism 22 which, when the upper platen 1 is raised or, when the upperplaten 1 is moved apart from the moving platen, automatically providesfor the two portions 15 a and 15 b forming the lips to be separated andwidened out. Now, if the portions are widened out (in order to allow forthe neck portion of the preform to be knocked out), it would bepractically impossible to simply bring the moving platen 2 to a rest onthe cavity-carrying platen 4, since the lip portions 15 a and 15 b wouldinterfere violently against the upper edge of the respective cavities,thereby getting damaged and/or damaging the cavities themselves.

An obvious solution lies therefore in providing an appropriate removablemember between the platens in such a manner as to adequately move andkeep the platens apart from each other at a desired distance “Z” that iseffective in doing away with the above described drawback.

In a preferred manner, the removable member is constituted by amultiplicity of resting cylinders 16, or parallelepipeds, arrangedparallel to each other and having the same height, the axis of which isparallel to the direction of movement of the moving mould-carryingplaten, as this is illustrated in the Figures.

With reference to FIG. 7, it furthermore turns out to be of particularadvantage if the removable member is applied to rest upon thecavity-carrying platen 4. In view of a safer, more reliable engagementand centering of the member (cylinders) 16 with and relative to themoving platen 2 when the mould is clamped into its closed position, themoving platen 2 itself is provided, in correspondence of the restingzones of the lower surface 18 thereof, with appropriate recessed seats17 adapted to be coupled with an upper portion 19 of a respectiveremovable member (cylinders). One of ordinary skill in the art wouldreadily recognize that the removable member is to be used as describedabove to separate the movable platen and the lower cavity-carryingplaten when the injection machine is not in operation.

Similarly, the cavity-carrying platen 4 is provided, on the uppersurface thereof, with corresponding recessed seats 17A adapted to becoupled with the lower portions 19A of respective removable means(cylinders).

Those skilled in the art will at this point be fully capable of seeingclearly into the method involved in the implementation and utilizationof the present invention. Such a method can be shortly set forth asincluding the steps of:

separating a moving mould-carrying platen 2, associated to and joinedwith a respective upper platen 1, from the lower cavity-carrying platen;

placing the removable member (cylinders) 16 between the movingmould-carrying platen 2 and the cavity-carrying platen, by preferablyusing the recessed seats 17 and 17A for this purpose;

lowering the moving platen 2 towards the cavity-carrying platen 4 downto the point at which the moving platen 2 eventually comes to rest uponthe removable member;

separating and raising the upper platen 1 from the moving mould-carryingplaten 2, which remains resting on the removable member 16.

1. An injection moulding machine for forming preforms, comprising: anupper platen; a moving platen operable to be moved relative to saidupper platen, said moving platen having through-holes; a support barconnected to said moving platen and carrying a plurality of lips, eachof said lips comprising a pair of separable members; a plurality of malemembers connected to said upper platen by fastening means; cooling tubesinserted into said male members; a lower cavity-carrying platen having aplurality of cavities corresponding to respective nozzles, said lowercavity-carrying platen having through-holes; a plurality of guidecolumns fixed to and extending from said upper platen so as to beslidably insertable into said through-holes in said moving platen andinto said through-holes in said lower cavity-carrying platen, said guidecolumns being completely disengageable from said moving platen and saidlower cavity-carrying platen; and a removable member to be arrangedbetween said moving platen and said lower cavity-carrying platen so asto position said moving platen with respect to said lowercavity-carrying platen and maintain a pre-selected distance between saidmoving platen and said cavity-carrying platen.
 2. The injection mouldingmachine of claim 1, wherein said guide columns are completelydisengageable from said moving platen and said lower cavity-carryingplaten and said removable member is operable to be arranged between saidmoving platen and said lower cavity-carrying platen when said injectionmoulding machine is not in operation.
 3. The injection moulding machineof claim 1, wherein said removable member comprises a plurality ofresting cylinders arranged parallel to each other and having the sameheight, a longitudinal axis of each of said resting cylinders beingparallel to a direction of movement of said moving platen.
 4. Theinjection moulding machine of claim 3, wherein said resting cylindersare shaped so as to rest upon said lower cavity-carrying platen.
 5. Theinjection moulding machine of claim 3, wherein said moving platen hasrecessed seats on a lower surface thereof for coupling to an upperportion of said resting cylinders, and said lower cavity-carrying platenhas recessed seats on an upper surface thereof corresponding to saidrecessed seats of said moving platen for coupling to a lower portion ofsaid resting cylinders.
 6. The injection moulding machine of claim 3,wherein said resting cylinders comprise a plurality of separate,non-axially arranged cylinders spaced apart between an upper surface ofsaid lower cavity-carrying platen and a lower surface of said movingplaten.
 7. The injection moulding machine of claim 1, wherein saidremovable member comprises a plurality of separate, parallel, andnon-axially arranged resting cylinders spaced apart between an uppersurface of said lower cavity-carrying platen and a lower surface of saidmoving platen.
 8. The injection moulding machine of claim 1, whereinsaid removable member is shaped so as to rest upon said lowercavity-carrying platen.
 9. The injection moulding machine of claim 1,wherein said moving platen has recessed seats on a lower surface thereoffor coupling to an upper portion of said removable member, and saidlower cavity-carrying platen has recessed seats on an upper surfacethereof corresponding to said recessed seats of said moving platen forcoupling to a lower portion of said removable member.
 10. A method ofremoving and re-assembling male members in an injection mouldingmachine, comprising: separating a moving platen, joined with an upperplaten, from a lower cavity-carrying platen, the injection mouldingmachine having guide members fixed to and extending from the upperplaten and slidably inserted into through-holes in the moving platen andinto through-holes in the lower cavity-carrying platen so as to engagethe moving platen and the lower cavity-carrying platen; positioning aremovable member between the moving platen and the lower cavity-carryingplaten so as to limit travel of the moving platen towards the lowercavity-carrying platen, and so that the moving platen can be positioneda pre-selected distance from the lower cavity-carrying platen; loweringthe moving platen towards the lower cavity-carrying platen to a positioncorresponding to the pre-selected distance so that the moving platencomes to rest upon the removable member; and separating and raising theupper platen from the moving platen so that the moving platen remainsresting on the removable member, and so that the guide columns arecompletely disengaged from the moving platen and the lowercavity-carrying platen.
 11. The method of claim 10, wherein saidpositioning of the removable member is conducted when the injectionmoulding machine is not in operation.
 12. The method of claim 10,wherein said positioning of the removable member comprises positioning aremovable member including a plurality of resting cylinders arrangedparallel to each other and having the same height, a longitudinal axisof each of the resting cylinders being parallel to a direction ofmovement of the moving platen.
 13. The method of claim 12, wherein thelower cavity-carrying platen has recessed seats in an upper surfacethereof, said positioning of the removable member comprises arrangingthe resting cylinders so that a lower portion of each of the restingcylinders is coupled to a respective one of the recessed seats in theupper surface of the lower cavity-carrying platen, and wherein themoving platen has recessed seats in a lower surface thereof, saidlowering of the moving platen comprising lowering the moving platen sothat an upper portion of each of the resting cylinders is coupled to arespective one of the recessed seats in the lower surface of the movingplaten.